The "minimum throttle" was a concern for at least 20 model years. By 2011 the symptoms changed a little, so not every vehicle acts the same way. Also, since the throttle-by-wire systems came around, it is even less of an issue, but we still need to be aware of it. The important point to remember is if a battery cable is disconnected or if the Engine Computer is unplugged, don't be worried about any new symptoms that show up related to idle speed or stalling. Just be aware there is likely to be a specific set of conditions that must be met for the relearn to take place, and those conditions should be met during normal driving conditions. For the older vehicles, the computer needed to know your foot was off the accelerator pedal. To do that, it wanted to see a rock-solid signal voltage from the throttle position sensor, but you could achieve that with your foot on the pedal, so it wanted to see that for at least seven seconds. That would be nearly impossible to do with your foot. Next, it needed to know you had been pushing the accelerator pedal and it's released now. It does that by seeing the high manifold vacuum from the MAP sensor. You can achieve that by snapping the throttle and immediately releasing it, but that sharp rise in vacuum only lasts one or maybe two seconds. The only way to get really high vacuum for seven seconds is during coasting from highway speed. When those conditions are met, the computer records the signal voltage from the throttle position sensor and puts that in memory. From then on, any time it sees that same voltage, it knows it has to be in control of idle speed. At all other times it leaves engine speed up to you.
On later models, to reduce the complaints of low idle speed after other repairs or services, the Engine Computers have been programmed to keep idle speed up higher until everything is relearned, so the conditions under which you might notice symptoms can be different.
When the starter is intermittent, the most common cause is burned / arced-away contacts inside the solenoid. This relates to the little silver Nippendenso starters used on Chryslers and Toyotas. The problem was so common, many hardware stores and farm and home stores have repair kits that include more parts than needed. By 2011, Chrysler had switched to a Bosch design, so this too is less of an issue. It's still worth mentioning. The symptom will be the starter drive makes one loud clunk when the ignition switch is turned to "crank", but the starter doesn't spin the engine. You have to release the switch, then try again, multiple times, before a good spot rotates around on the contact and the starter works. That problem gets worse over time as the contacts continue to arc away. In the case of my mother's '95 Grand Caravan, she lost count after 700 tries and a blister on her thumb, but it did finally crank and the engine started. I had ignored that for over six months, but you can be sure I heard about it that night!
You won't hear that single, loud clunk from the starter when it is cranking the engine normally because the spinning starter is so much louder.
The burned contacts reduce the amount of current that can get through to run the starter motor. One of the common observations, or clues, was it was more likely to successfully crank the engine with a jump-start or with a larger battery charger connected. Either of those raises system voltage higher than that of just the vehicle's battery. That higher voltage causes higher current to want to flow, and that is often just enough to get the starter up and running.
One thing that has me confused is your comments about moving the negative cable to the body. This brings back nightmares of me trying to diagnose a friend's '69 Barracuda for an intermittent failure to crank. It wasn't until the throttle cable started smoking that the error of my ways became evident. He had the fat negative battery cable bolted to the left inner fender. Since the engine, transmission, rear axle, and exhaust system are all mounted on rubber mounts, hangers, and bushings, the throttle cable was the only path the starter current could find to get back to the battery, and there's no way that could handle 150 amps. That fat cable has to be bolted to the engine block or transmission. Every negative battery cable has a second, smaller wire that is bolted to the body. That's for the return path for the lighting and other circuits. If you have that fatter cable bolted to the body, it is only by luck that the starter works at all. There's often one or more braided ground straps between the firewall and the engine, but those are to address radio interference noise. They might handle starter current, but that isn't what they're there for.
To be sure we're talking about the same thing, please list the exact symptoms again and any additional observations or clues. Turn on the head lights and see what happens to their brightness when the starting problem occurs. If they go dim, have a helper run the ignition switch while you measure the battery's voltage, but put the meter's probes on the cable clamps right next to the battery's posts, not on the posts themselves. You'll be starting with 12.6 volts. When the starter works, that voltage will not drop below 9.6 volts if all the connections are good. When the starter doesn't work, the voltage you find between those two cable clamps will tell us where to go next.
If the engine does always crank normally, but at times fails to run, hold the accelerator pedal down 1/4". If that makes the engine start right up, the minimum throttle relearn is the issue.
Another possibility is a leaking injector can cause low fuel pressure during starting. That pressure should hold for weeks, but if an injector is leaking, which isn't uncommon at higher mileages, it can bleed down in as little as perhaps 15 minutes after stopping the engine. When you turn the ignition switch on, the fuel pump runs for one second to insure fuel pressure is up for starting in case it has dropped off a little. If a leaking injector caused pressure to drop too far, that one second isn't enough time to get the pressure back up. To add to the misery, while the pump resumes running during engine rotation, cranking in this case, the starter draws the battery's voltage down, and that is the same low voltage the runs the fuel pump. That means the pump runs slower than normal during cranking. You start with low fuel pressure, then the firing injectors bleed it off faster than it can build back up. That results in a strong starter cranking the engine, but the engine either won't run or sputters slowly to life. To get a clue this is the cause of a crank / no-start, turn the ignition switch to "run", wait until the fuel pump stops running after that initial one second, turn the switch back off, then turn it on a second time, or maybe even a third time, then crank the engine. The pump will run one second each time you do that. That will insure fuel pressure is high enough for starting. If that works every time, you can verify this by connecting a fuel pressure gauge to see if pressure drops over time when the engine is off.
A failing fuel pump is another possibility, but it doesn't really fit with the symptoms you described. First, listen for the hum of the fuel pump for one second when you turn the ignition switch to "run". If you're able to hear that hum, the pump is okay. Unlike GM fuel pumps that always start up, then leave you sitting on the side of the road later, Chrysler pumps almost always fail to start up when they're failing, leaving you sitting in your driveway. This is due to worn brushes in the pump's motor. Once a Chrysler fuel pump is running, it rarely stops running while you're driving. Here again, worn brushes might make the pump run too slowly, but a jump-start and the resulting higher voltage can be just enough to get it going. Once it's up to speed, normal vibration of the motor keeps the brushes making contact as long as the engine is running.
Let me know if this helps and where we should go next.
Tuesday, October 27th, 2020 AT 5:36 PM
